Blends of olefin polymer and nitrile rubber are known. For example, see U.S. Pat. Nos. 3,909,463 and 4,104,210. Olefin polymers and nitrile rubber are largely incompatible with one another. Mutual incompatibility prevents the development of optimum properties in blends of these materials. Thus, if the compatibility of the blend components can be increased, improved blends may be obtained. This is because particles of one or another component in the blend will be smaller and less likely to act as flaws.